In an automotive vehicle, it is known to utilize a gearshift lever or an electrical control in order to select a ratio or a function of a gearbox (forward, rear, neutral, parking brake . . . ). This gearshift lever or this electrical control operates a drive shaft connected to the gearbox in order to place it in the position corresponding to the function or to the selected ratio.
It is known to use a sensor for measuring the position of the shaft in order to permit the management of the engine parameters by an electronic control unit of the vehicle. Such a sensor measures the position of the shaft and then transmits this information to the electronic control unit of the vehicle in order to deduce therefrom in particular the engaged ratio or the function of the gearbox. This positional information may be utilized, for example, in order to display the function or the ratio selected by the user.
In the case of an automatic gearbox, in which the shaft moves in a single direction, the position sensor that is used is a linear sensor. In an existing solution, as illustrated in FIG. 1, this sensor 1 is of the inductive type and comprises one transmitting coil 2 and two receiving coils 3, 4 making it possible to detect the position of a target mounted on the shaft, the target passing in front of the sensor in a direction X, by performing measurements of inductive effects between the transmitting coil 2 and the receiving coils 3, 4. These effects are due to the modification of the magnetic coupling between the transmitting coil 2 and each receiving coil 3, 4 when the target is situated in the detection zone of the sensor 1. Thus, by measuring the electrical voltages at the terminals of the receiving coils 3, 4, it is possible in a manner known per se to deduce the precise position of the target. Although such a sensor 1 may be appropriate in the case of an automatic gearbox, it exhibits the disadvantage of determining the position of the shaft in only a single direction X.
In the case of a manual gearbox, however, the positions corresponding to the gear ratios are generally disposed in two ranges and in one position, referred to as the neutral position, situated between these two ranges and not corresponding to the selection of any ratio. As a result, in view of the selection of the ratios by the user, the shaft is, on the one hand, in linear movement in its longitudinal axis when the user moves the gearshift lever from one range of ratios to the other and, on the other hand, in angular movement when the user selects a ratio in the same range. Also, given that the shaft is guided by the gearshift lever both in translation and in rotation, it is necessary to be aware of its position in both directions.
For this purpose, a system comprising a matrix of Hall-effect sensors disposed in two directions in order to form a detection zone in two dimensions is familiar. However, such a system exhibits a number of disadvantages. First of all, the use of a matrix of sensors makes it possible to determine the position of the shaft only in a discrete manner, which restricts the accuracy of the system to the position of each sensor. In addition, the use of a plurality of sensors significantly increases the complexity and the cost of the system while reducing its reliability. Such a matrix also requires a suitable microcontroller for collecting and processing all of the data supplied by each sensor in order to deduce therefrom the position of the target, which makes the system more complex and costly. Finally, the zones between the sensors are so-called sensitive zones, because a target situated between two sensors may not be detected by the matrix, which leads to a malfunctioning of the system and accordingly presents a major disadvantage.